Executive task-set inertia manifests via response suppression and not vector inversion

Abstract

Alternating between different tasks represents an executive function essential to daily living. In the oculomotor literature reaction times (RT) for a 'standard' stimulus-driven (SD) prosaccade (i.e., saccade to veridical target location at target onset) increase when preceded by a 'non-standard' antisaccade (i.e., saccade mirror-symmetrical to target location at target onset), whereas the converse does not elicit a switch-cost. The prosaccade switch-cost has been attributed to lingering neural activity – or task-set inertia – related to prosaccade suppression (i.e., response suppression) and decoupling stimulus-response spatial relations (i.e., vector inversion). It is, however, unclear whether response suppression and/or vector inversion contribute to this switch-cost. Here, Experiment 1 had participants alternate (i.e., AABB paradigm) between minimally delayed (MD) pro- and antisaccades. MD saccades require responses after target extinction necessitating response suppression across pro- and antisaccades – used to determine whether vector inversion contributes to a task-set inertia. In Experiment 2, participants alternated between SD pro- and MD antisaccades to determine if a task switch-cost is selectively imparted when a stimulus-driven and standard response is preceded by a non-standard response. Experiment 1 showed that RTs for MD pro- and antisaccades were not influenced by the preceding trial-type; i.e., vector inversion did not engender a switch-cost. Experiment 2 showed that RTs for SD prosaccades were increased when preceded by a MD antisaccade. Accordingly, the executive demands of response suppression engendered a task-set inertia for a subsequent stimulus-driven and standard response (i.e., SD prosaccade) – a finding supporting the view that response suppression is a hallmark feature of executive function.

Acknowledgments: Natural Sciences and Engineering Research Council (NSERC)